Patients who are artificially respirated in an intensive care unit receive breathing air, which is adapted to the physiological needs of the patient in terms of temperature and humidity. Active humidifiers, which heat and humidify the breathing gas, are used for this. A water-filled container, through which the gas to be inspired is sent and is enriched with moisture, is located within the humidifier. The breathing tubes are usually provided with a tube heater to prevent condensation of moisture within the breathing tube system.
A breathing tube with resistance wires arranged helically on the outside is known, for example, from U.S. Pat. No. 5,357,948. One or two resistance wires are provided, which extend helically on the outside of the breathing tube. Furthermore, a separate, non-heatable conductor for the return line is located on the outside. The resistance wires may be connected either in series or in parallel, the resistance wires being contacted electrically via a tube end.
The drawback of the prior-art breathing tube is that short-circuit may develop within the forward line and the return line in case of damage to the insulation of the resistance wires, which is possibly associated locally with intense heating of the tube. The tube may become damaged hereby, and leaks, through which breathing gas can escape, may also develop at such a site.